1. Field of the Invention
The present invention relates to a fuel injection valve installation structure of an engine. In the fuel injection valve installation structure, an installation hole is formed in an engine component member that constitutes a part of an engine. The installation hole has an annular shoulder portion, which is formed in the middle portion thereof, and which faces the exterior side. The fuel injection valve is held between the annular shoulder portion and a supporting member attached to the engine component member.
2. Description of Background Art
A type of four-cycle direct injection engine is disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-116447. The type of engine has an installation hole formed in a cylinder head. An air injector as a fuel injection valve is held between a supporting member attached to the cylinder head and an annular shoulder portion formed in the middle portion of the installation hole.
In the structure disclosed in Japanese Patent Application Laid-Open No. 2004-116447, the air injector is directly held between the cylinder head and a head cover. Thus, the vibration produced at the time of injection is emitted from the engine body to the outside. When an engine is mounted on a vehicle, some kind of countermeasure, such as a sound insulation cover is needed to deal with the emitted noise. More particularly, with regard to a motorcycle, such a sound insulation cover directly affects the appearance, and also affects the cooling capability of the engine itself. These problems must be taken care of. As a result, the structure becomes more complex, and the cost becomes higher.